Infection of Aphanius dispar (Holly, 1929) with Ligula intestinalis plerocercoids in Mehran River, Hormuzgan province, south of Iran

Aphanius dispar (Holly, 1929) (knowm as Mahi gour-e khari, mahi dom parchami, kopurdandandar-e balehbolband) is an euryhaline tooth-carp fish which apparently prefers brackish waters of coastal areas of Iran. It is also distributed in Cyprus, Iraq, Somalia, Israel, Saudi Arabia, Syria and Djibouti (Etemadfar et al., 1983) available at: www.fishbase.org, accessed in May, 2008). Aphanius dispar occurs in shallow water and among vegetation over sand, rock or soft detritus bottoms (Coad, 1996) at: www.briancoad.com). Ligula intestinalis (L., 1758) is a pseudophyllidean cestode which in its plerocercoid stage infects a range of freshwater fish species, particularly members of the cyprinidae, as its second intermediate host and it has a widespread distribution throughout the northern hemisphere (Dubinina, 1980). The plerocercoid stage is infective to a wide range of fish-eating birds, which serve as the final host. Ligula has been the subject of a number of studies, mainly those aimed at differences in pathogenicity and parasite-host relationships (Arme et al., 1983). The parasite-host relation parameters were studied in many fish species including Abramis brama, Blicca bjoerkna (Barus and Prokes, 2002), Rutilus rutilus (Kennedy et al., 2001) and Tinca tinca (Ergonul and Altindag, 2005). Jalali (1998) reported Ligula intestinalis infection in some native fishes of Iranian basins in the north and south of the country, from ship sturgeon of the Caspian Sea (Mousavi et al., 2000) and from river whitefishes in Aras Dam (Yousefi et al., 2005). Karemi et al. (2006) investigated the procercoid of L. intestinalis from copepods in Satarkhan Dam, East Azarbaijan Province, north-western Iran. In the Middle East, Rahemo and Al-Nouri (1999) evaluated the effect of L. intestinalis on gonad histology of Acanthobrama marmid in Iraq. However, no report is available on the occurrence of L. intestinalis from tooth-carp fish found in southern Iran. Recently, the present authors studied the infection of A. persicus in Barme-e-Shoor Spring-Stream System, Maharlu Basin, Shiraz, Iran (Unpublished data). The present study was undertaken to investigate the possibility of A. dispar acting as an intermediate host for Ligula intestinalis from Mehran river (27?3?14.20?N- 54?20?40.26? E,) in Mehran basin, near Bastak city, Hormuzgan Province, south of Iran. The water is clear and runs slowly in summer but it is floody in winter. We dissected a total of 63 A. dispar (Fig. 1) found in this river using dip net and preserved them in 10% formalin until examination. Total length (TL), standard length (SL) of the collected specimens, total length of parasites nearest to.05 mm using vernier caliper and weight of parasites nearest to 0.001 g (total weight, TW) were measured. The fish were dissected; the body cavity and viscera were examined to determine the presence of the parasite. Prevalence (%) was calculated according to the percent of infected fish divided by the total number of fish. Mean intensity was determined by dividing the total number of collected parasites to the number of infected fish samples, while abundance was calculated by dividing the total number of collected parasites to the total number of examined fish. Mean length and weight of fish and parasites were compared statistically using analysis of variance in SPSS version 11.5 for windows. In this survey, 31 males and 32 females (total and standard length ranging from 24.6-54.1 mm and 20.5-45.3 mm respectively) were collected in July 2003 of which 14 specimens (22.22 %) including 4 males and 10 females were infected. The morphology of the infected fish was normal but their abdomen appeared distended and hard. However, the plerocercoids of L. intestinalis coiled around the viscera and occluded the body cavity (Fig. 2). From 63 dissected fish only two fish were infected with 4 and 3 parasites respectively and the others had only one parasite. The maximum and minimum of parasite lengths were 64.2 mm and 22.7 mm respectively. Also the maximum and minimum of parasite weights were 0.3 and 0.047 g respectively (Table 1). Mean parasite length and weight were 41.48 mm and 0.19 g respectively. Althought the total length of male and female fish was not significantely different, the total length of parasites in male and female fish was significantly different (P < 0.05). No significant difference was observed when the weight of male and female fish and their parasites were compared. The prevalence, intensity and abundance of infection by pleurocercoid of L. intestinalis were 22.22%, 1.36 and 0.3 respectively.